Transplacental MeAIB and glucose clearance with respect to maternal dietary protein content at days 16 and 19 of mouse pregnancy (n= &gt; 9 litters per group).<\#13>

Values within columns with different letters (a b) are significantly different from each other P&lt;0.05

Maternal diet during pregnancy is important in determining placental development. In farm animals, maternal undernutrition alters placental nutrient transfer but little is known about the effects of manipulating dietary composition on placental function in any species (1). This study examined transplacental transfer of nutrients transported by facilitated diffusion (14C-methyl-D-glucose) and active transport (14C-methyl aminoisobutyrate, MeAIB) in mice fed diets with varying protein content throughout pregnancy (term = 20 days, d). Group-housed pregnant mice were fed ad libitum either 23% (C23; n=66), 18% (C18; n=83), or 9% (C9; n=70) casein diets made isocalorific by carbohydrate supplementation. At 16d and 19d, mice were anaesthetised (10ul/g fentanyl-fluanisone:midazolam:water, 1:1:2, ip) before in vivo measurement of unidirectional materno-fetal flux of each tracer (2). After maternal cervical dislocation, placentas and fetuses were weighed. Fetuses were decapitated and dissolved in Biosol for scintillation counting. Transplacental tracer clearance was calculated as µl.min-1.g-1 placenta using maternal plasma and accumulated fetal radioactivity (3). All procedures for carried out under the Animal (Scientific Procedures) Act 1986. Results are means ± SE. Statistical significance was assessed by one way ANOVA. MeAIB clearance in the C9 group matched the C23 group, both having significantly greater clearance than the C18 group at each age (Table 1). However, at E16, glucose clearance was greater in the C9 and C18 groups than the C23 group (Table 1). By E19, glucose clearance was greatest in the C9 group with both C18 and C23 groups transferring significantly less (Table 1). The results show that maternal dietary composition alters placental nutrient transport capacity with differential effects on MeAIB and glucose transport in late gestation. Upregulation of placental glucose transfer in the mice fed the lowest protein diet may help meet fetal nutrient demands for growth. Variations in the relative proportions of nutrients supplied to the fetus due to dietary-induced adaptations in placental nutrient transport may programme tissue development in utero with consequences long after birth (1).